Pressurized containers such as inhalers may need to be packed in impermeable packages to prevent atmospheric moisture ingress. The use of such impermeable packages can cause accumulation of propellant gases that gradually leak from the pressurized container and may eventually lead to failure of the seals of the package. This problem becomes more prominent when traditional propellants chlorofluorocarbons (CFCs) are replaced by hydrofluoroalkane propellants (such as HFA-134a and HFA-227) for environmental reasons.
U.S. patent Nos. 6,179,118B1, 6,119,853 and 6,352,152 address this problem by using a flexible package that is “impermeable to moisture and permeable to the propellant.” While this appears to be a good approach, applicants had much difficulty in fabricating a flexible wrapping material which is impermeable to moisture and permeable to the propellant so that the resulting package would operate similar to “a virtual one-way valve”. Presumably, fabricating such flexible wrapping materials is much more technically involved and more costly than it appears from reading the aforementioned patents. Therefore, there is a need for a simpler and more understandable way to solve the inflation problem in packing pressurized containers.
Furthermore, the ability of the packages disclosed in U.S. Pat. Nos. 6,179,118 B1, 6,119,853 and 6,352,152, to prevent gas build up in the packages, would appear to be limited by the permeability of the wrapping material to the propellant and the rate at which the propellant is released from the container.
Therefore, there is a need for an enhanced drug product comprising a package that is impermeable, or substantially impermeable, to the egress of HFA gas from within the package, and still is capable of maintaining the enclosed volume of the sealed package at about ambient pressure when any leakage of HFA gas propellant occurs.